Glenoid implant anchor post

ABSTRACT

A prosthesis that mechanically couples with both cancellous bone and cortical bone of a glenoid includes a head portion comprising a rear surface and an articular surface, an anchor member, and a plurality of deformable fins extending radially outward from the anchor member. The anchor member includes a distal end and a proximal end connected to the rear surface of the head portion. The plurality of deformable fins extend radially outward from the anchor member and includes at least a first proximal fin adjacent to the rear surface of the head portion positioned to engage with the cortical bone. The anchor member may also include at least one distal fin located proximate the distal end of the anchor member positioned to engage with the cancellous bone.

TECHNICAL FIELD

The present invention relates generally to an apparatus and device forsecuring a glenoid implant to a glenoid, and in particular, to an anchorwith deformable portions that are adapted to form a cement-lessconnection with the glenoid.

BACKGROUND OF THE INVENTION

In a healthy shoulder joint, the humeral head of the humerus interactswith the glenoid of the scapula to form a “ball and socket” joint. Thehumeral head abuts and articulates with the glenoid to allow a widerange of motion in the shoulder. In an unhealthy shoulder joint, theinteraction between the glenoid and the humerus are compromised,requiring repair or replacement. Total shoulder replacement is onemethod used to replace shoulder joints that have been damaged beyondrepair due to trauma or disease. Typically, a total shoulder replacementprocedure includes providing a glenoid component and a humeral componentthat interact with each other at an articulating surface.

Conventionally, glenoid components have been designed as two-piececomponents made of plastic and metal. Due to difficulties in designing amechanism to lock the two pieces together, the assembly can fail overtime. Replacement of the glenoid component requires that the patientundergo an additional surgical procedure and be subjected to additionalrecovery time and costs. One-piece glenoid components have also beendeveloped that fixate to a glenoid and provide an articulating surfacefor the humeral component. Bone cement is commonly used to secure theglenoid component to the glenoid for both two-piece and one-piececomponents.

U.S. Pat. No. 6,911,047 (Rockwood Jr. et al.) discloses a glenoidcomponent having an anchor peg and stabilizing pegs to secure theglenoid component to a glenoid without the use of bone cement. Theanchor peg disclosed in Rockwood Jr. et al. includes a body portionhaving a plurality of fins at a proximal end of the body portion. Whenthe glenoid component is positioned within the glenoid and scapula, thefins provide resistance to removal forces on the glenoid component. Thestabilizing pegs are positioned within the glenoid around the anchor pegto prevent movement of the body portion relative to the glenoid.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to a prosthesis with an anchor havingdeformable portions that engage with cortical bone at a glenoid.

In some embodiments, the present prosthesis is adapted to form acement-less connection with a glenoid. The deformable portions areoptionally structured for substantially unidirectional deformation. Thatis, the deformable portions resist deformation in the direction ofremoval. The anchor is optionally modular so that it is easilycustomized for patients of varying sizes. For example, differentpatients may have cortical bone of varying thicknesses and/or glenoidsof varying depths.

In one embodiment, the present invention is a prosthesis thatmechanically couples with both cancellous bone and cortical bone of aglenoid. The prosthesis includes a head portion comprising a rearsurface and an articular surface, an anchor member, and a plurality ofdeformable fins extending radially outward from the anchor member. Theanchor member includes a proximal end and a distal end. The proximal endis connected to the rear surface of the head portion. The plurality ofdeformable fins extend radially outward from the anchor member andinclude at least a first proximal fin adjacent to the rear surface ofthe head portion positioned to engage with the cortical bone. Theplurality of deformable fins may also include at least one distal finlocated proximate the distal end of the anchor member positioned toengage with the cancellous bone.

In another embodiment, the present invention is a prosthesis forsecurement to a glenoid and includes a head portion and an anchor. Thehead portion has a first surface and a second surface. The anchorextends from the first surface of the head portion and includes aproximal end connected to the first surface of the head portion, adistal end opposite the proximal end and a set of proximal fins. The setof proximal fins extend radially from the proximal end of the bodyportion. The anchor may also include a set of distal fins extendingradially from the distal end of the body portion. The anchor isconfigured to engage the glenoid.

In an alternative embodiment, the present invention is an implantpositionable between a glenoid and a humeral component. The implantincludes a head portion and an anchor. The head portion has a firstsurface engageable with the glenoid and a second surface engageable withthe humeral component. The anchor extends substantially perpendicularlyfrom the first surface of the head portion and has a first end attachedto the first surface, a second end opposite the first end, and a firstset of flexible flanges positioned proximate the first end of theanchor. The anchor may also include a second set of flexible flangespositioned proximate the second end of the anchor.

The present invention is also directed to a method of fixating aprosthesis to a glenoid. The method includes aligning an anchor of theprosthesis with a bore formed in the glenoid and inserting the anchor inthe bore such that a first surface of the prosthesis engages theglenoid. The anchor includes a first deformable fin and a seconddeformable fin. The first deformable fin is implanted within cancellousbone and the second deformable fin is implanted proximate cortical bone.

Terminology such as “first,” “second,” “third,” etc., is used herein todesignate particular components being described. Because variouscomponents of the embodiments described herein can be positioned in anumber of different orientations and in a number of different sequences,this terminology is used for the purposes of illustration and is notintended to be read in a restrictive manner.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded view of a glenoid component positioned between aglenoid and a humeral component in accordance with an embodiment of thepresent invention.

FIG. 2 is a perspective view of the glenoid component in accordance withan embodiment of the present invention.

FIG. 3 is a side view of the glenoid component implanted in the glenoidin accordance with an embodiment of the present invention.

FIG. 4 is a side view of an alternative glenoid component in accordancewith an embodiment of the present invention.

FIG. 5 is a perspective view of an alternative glenoid component inaccordance with an embodiment of the present invention.

FIG. 6 is a perspective view of an alternative glenoid component inaccordance with an embodiment of the present invention.

FIG. 7A is a perspective view of an alternative glenoid component inaccordance with an embodiment of the present invention.

FIG. 7B is a side view of the alternative glenoid component of FIG. 7Ain accordance with an embodiment of the present invention.

FIG. 8 is a perspective view of an alternative glenoid component inaccordance with an embodiment of the present invention.

FIG. 9A is a perspective view of an alternative glenoid component inaccordance with an embodiment of the present invention.

FIG. 9B is a side view of a stepped hole configuration in accordancewith an embodiment of the present invention.

FIG. 9C is a side view of the alternative glenoid component of FIG. 9Apositioned within the stepped hole configuration of FIG. 9B inaccordance with an embodiment of the present invention.

FIG. 10 is an exploded side view an alternative glenoid component inaccordance with an embodiment of the present invention.

FIG. 11 is a graph of load versus displacement during insertion of theglenoid component in accordance with an embodiment of the presentinvention.

FIG. 12 is a graph of load versus displacement during removal of theglenoid component in accordance with an embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an exploded view of a glenoid component 10 positionedbetween a glenoid 12 of a scapula S and a humeral component 14. Whilethe humeral component 14 illustrated in FIG. 1 is a prosthesis, thepresent glenoid component 10 can also engage with an anatomical humeralhead. Therefore, reference to the humeral component 14 herein should beconstrued to include an anatomical humeral head.

The glenoid component 10 is attachable to the glenoid 12 and functionsas an artificial surface for engagement with the humeral component 14.The glenoid component 10 can be secured to the scapula S without the useof bone cement and provides structural resistance from being removedfrom the scapula S.

The glenoid component 10 includes a head portion 16, an anchor 18, afirst stabilizing pin 20 a, a second stabilizing pin 20 b and a thirdstabilizing pin 20 c (collectively referred to as “stabilizing pins20”). The head portion 16 includes a first articulating surface 22 and asecond surface 26. The first articulating surface 22 engages the humeralhead 24 of the humeral component 14, which includes a stem 28 implantedin a humerus H, to allow rotation and movement of a shoulder.

The anchor 18 and stabilizing pins 20 of the glenoid component 10 extendfrom the second surface 26 of the head portion 16 of the glenoidcomponent 10 and secure the glenoid component 10 to the glenoid 12. Inthe illustrated embodiment, the glenoid 12 and scapula S include ananchor hole 30 and a plurality of stabilizing holes 32 a, 32 b, 32 c(referred to collectively as “32”) to accept the anchor 18 and thestabilizing pins 20, respectively. In an alternate embodiment, thepresent glenoid component 10 can be implanted without the pre-drilledholes 30, 32.

Referring more particularly to FIG. 2, but still also in reference toFIG. 1, FIG. 2 shows a perspective view of the glenoid component 10,which functions to provide a replacement surface to articulate with thehumeral component 14. The first articulating surface 22 of the headportion 16 is concave and configured to engage the humeral head 24 ofthe humeral component 14. The first articulating surface 22 is thusformed to accept at least a portion of the humeral head 24 within theconcavity of the first articulating surface 22. The second surface 26 ofthe head portion 16 is preferably configured with the same shape as theglenoid 12 of the scapula S, which is usually convex.

In the illustrated embodiment, the anchor 18 extends substantiallyperpendicularly from the second surface 26 of the head portion 16 andsecures the glenoid component 10 to the glenoid 12. In otherembodiments, the anchor 18 may extend at various other angles relativeto the second surface 26 of the head portion 16. The anchor 18 ispreferably positioned substantially at the center of the second surface26 of the head portion 16 and is in the form of a cylindrical shaft 34having a proximal end 36, a middle section 38 and a distal end 40. Theshaft 34 is attached to the head portion 16 at the proximal end 36 andtapers at the distal end 40 to facilitate insertion of the anchor 18into the anchor hole 30 of the glenoid 12. In one embodiment, the distalend 40 of the anchor 18 includes a conical tip, or other shape thatfacilitates insertion into the glenoid 12, with or without thepre-drilled hole 30. Alternatively, the anchor 18 can have a tapered orstepped structure.

In the illustrated embodiment, the anchor 18 has a substantiallyconsistent diameter. Distal fins 44 extend radially outward from thedistal end 40 of the shaft 34 and proximal fins 42 extend radiallyoutward from the proximal end 36 of the shaft 34. In the illustratedembodiment, the set of proximal fins 42 includes a first proximal fin 42a and a second proximal fin 42 b. The set of distal fins 44 includes afirst distal fin 44 a, a second distal fin 44 b, a third distal fin 44 cand a fourth distal fin 44 c.

In the illustrated embodiment, the sets of distal fins 44 and proximalfins 42 are spaced from each other by the middle section 38 of the shaft34. In an alternate embodiment, the sets of proximal and distal fins 42,44 extend the full length of the shaft 34 without being separated by themiddle section 38.

Both sets of proximal and distal fins 42, 44 are flexible and areconfigured to bend or deform when force is exerted against them.Deformation of the proximal and distal fins 42 a, 42 b, 44 a, 44 b, 44c, 44 d can be plastic or elastic. For example, in one embodiment, theproximal and distal fins 42 a, 42 b, 44 a, 44 b, 44 c, 44 d deformplastically upon insertion into the glenoid 12 and retain a generallycurved configuration, such as illustrated in FIG. 3. Alternatively, theproximal and distal fins 42 a, 42 b, 44 a, 44 b, 44 c, 44 d return totheir un-deformed configuration after implantation.

In the illustrated embodiment, the proximal and distal fins 42 a, 42 b,44 a, 44 b, 44 c, 44 d have substantially the same diameter.Consequently, the proximal and distal fins 42 a, 42 b, 44 a, 44 b, 44 c,44 d are co-axial with each other and the outside edges are aligned.Although FIG. 2 depicts the set of proximal fins 42 as including twofins 42 a, 42 b and the set of distal fins 44 as including four fins 44a, 44 b, 44 c, 44 d, the sets of proximal fins and distal fins 42, 44may include any number of fins.

In one embodiment, the shaft 34 and the proximal and distal fins 42 a,42 b, 44 a, 44 b, 44 c, 44 d of the anchor 18 are integrally formed withthe head portion 16. For example, the glenoid component 10 can be moldedas a single unitary structure or machined from a monolithic piece ofmaterial. In another embodiment, the shaft 34 and the proximal anddistal fins 42 a, 42 b, 44 a, 44 b, 44 c, 44 d are separate components(See e.g., FIG. 10). In an alternate embodiment, the proximal and distalfins 42 a, 42 b, 44 a, 44 b, 44 c, 44 d are molded from a first materialwhile the head portion 16 is molded from a second material. In thisembodiment the first material preferably has a higher stiffness than thesecond material.

The glenoid component 10 of the present application can be manufacturedfrom a variety of materials, such as for example polyethylene orultra-high molecular weight polyethylene (“UHMWPE”), such as disclosedin U.S. Pat. No. 6,911,047, the disclosure of which is incorporatedherein by reference.

The stabilizing pins 20 prevent the glenoid component 10 from movingrelative to the glenoid 12 once the glenoid component 10 is implanted inthe glenoid 12 and the scapula S. The stabilizing pins 20 preferablyextend substantially perpendicularly from the second surface 26 of thehead portion 16 and are positioned around the anchor 18. Each of thestabilizing pins 20 a, 20 b, 20 c includes a body 46 a, 46 b, 46 c(collectively referred to as “bodies 46”), respectively, having aproximal end 48 a, 48 b, 48 c (collectively referred to as “proximalends 48”), respectively, and a distal end 50 a, 50 b, 50 c (collectivelyreferred to as “distal ends 50”), respectively. Each of the bodies 46 ofthe stabilizing pins 20 is attached at its proximal end 48 to the headportion 16 of the glenoid component 10. The stabilizing pins 20optionally include an indent or series of indents 52 to accept and lockin bone cement, maintaining the stabilizing pins 20 in position.

The stabilizing pins 20 are preferably shorter than the anchor 18 and inone embodiment extend only slightly past the set of proximal fins 42 ofthe anchor 18. Similar to the distal end 40 of the anchor 18, the distalends 50 of the stabilizing pins 20 are also tapered to facilitateinsertion of the stabilizing pins 20 into the stabilizing holes 32 ofthe glenoid 12. In one embodiment, the distal ends 50 of the stabilizingpins 20 have a conical tip, or other shape that facilitates insertioninto the glenoid 12, with or without pre-drilled hole 32.

The stabilizing pins 20 may be arranged in any configuration on thesecond side 26 of the head portion 16 around the anchor 18. In oneembodiment, the stabilizing pins 20 are positioned such that the firststabilizing pin 20 a is positioned farther from the anchor 18 than thesecond and third stabilizing pins 20 b, 20 c. In another embodiment, thestabilizing pins 20 are positioned around the anchor 18 along aperiphery of the head portion 16 substantially equidistant from theanchor 18 and each adjacent stabilizing pin 20 a, 20 b, 20 c. AlthoughFIG. 2 depicts the glenoid component 10 as including three stabilizingpins 20, the glenoid component 10 may include any number of stabilizingpins, including zero, without departing from the intended scope of thepresent invention. When the glenoid component 10 does not include anystabilizing pins, any means for preventing rotation of the glenoidcomponent 10 relative to the glenoid 12 may be used. For example, theglenoid 12 may be milled in an oval shape and the glenoid component 10may be key implanted into the bone.

FIG. 3 shows a side view of the glenoid component 10 implanted throughthe glenoid 12 and into the scapula S. In practice, to attach theglenoid component 10 to the glenoid 12, the anchor hole 30 and theplurality of stabilizing holes 32 are preferably first drilled orotherwise formed in the glenoid 12. The anchor hole 30 is preferablysized to have a diameter D_(AH) slightly larger than a diameter D_(S) ofthe shaft 34 of the anchor 18 but smaller than a diameter D_(F) of thedistal and proximal fins 42 a, 42 b, 44 a, 44 b, 44 c, 44 d of theanchor 18. Because the proximal and distal fins 42 a, 42 b, 44 a, 44 b,44 c, 44 d are flexible, even though the diameters D_(F) of the proximaland distal fins 42 a, 42 b, 44 a, 44 b, 44 c, 44 d are larger than thediameter D_(AH) of the anchor hole 30, the proximal and distal fins 42a, 42 b, 44 a, 44 b, 44 c, 44 d can pass through the anchor hole 30 byexerting an extra amount of force on the glenoid component 10 andcausing the proximal and distal fins 42 a, 42 b, 44 a, 44 b, 44 c, 44 dto deform.

The stabilizing holes 32 are drilled around the anchor hole 30 and aresized to accept the stabilizing pins 20. The stabilizing pins 20 may bepress fit or interference fit into the stabilizing holes 32. Optionally,bone cement may also be utilized to help maintain the stabilizing pins20 within the stabilizing holes 32. If it is desired to use bone cementto aid in securing the glenoid component 10 to the glenoid 12, the bonecement can be applied at the indents 52 of the bodies 46 of thestabilizing pins 20 to increase the area of contact between thestabilizing pins 20 and the bone cement in order to increase the bond tosecure the stabilizing pins 20 within the stabilizing holes 32.

The anchor hole 30 and the stabilizing holes 32 are drilled such thatwhen the glenoid component 10 is positioned with respect to the glenoid12, the anchor 18 is aligned with the anchor hole 30 and the stabilizingpins 20 are aligned with the stabilizing holes 32. In one embodiment, adrill guide or pattern may be used to properly position and align theanchor hole 30 and the stabilizing holes 32 in the glenoid 12 tocorrespond with the positions and alignments of the anchor 18 andstabilizing pins 20 of the glenoid component 10, respectively.

After the anchor hole 30 and the stabilizing holes 32 have been formedin the glenoid 12 and the scapula S, the glenoid component 10 ispositioned in front of the glenoid 12 such that the anchor 18 andstabilizing pins 20 of the glenoid component 10 are aligned with theanchor hole 30 and the stabilizing holes 32, respectively, of theglenoid 12. As the glenoid component 10 is directed towards the glenoidsurface 12, the conical tip at the distal end 40 of the shaft 34 of theglenoid component 10 first enters the anchor hole 30. When the set ofdistal fins 44 contact the cortical bone 12 a, each of the distal fins44 a, 44 b, 44 c, 44 d deforms sequentially in order to pass through theanchor hole 30. Once the set of distal fins 44 are advanced past thecortical bone 12 a, they engage with the softer cancellous bone 12 b.

The distance “d” between the first proximal fin 42 a and the secondsurface 26 of the head portion 16 corresponds generally to the thicknessof the cortical bone 12 a. The distance “d” is generally between about 1to about 4 millimeters, and preferably between about 2 to about 3millimeters. In the embodiment of FIG. 10, the distance “d” isadjustable by substituting a different spacer 306.

The proximal fins 42 a, 42 b provide resistance against the smallerdiameter D_(AH) of the anchor hole 30 so enough force must be exerted inorder to engage the proximal fins 42 a, 42 b with the cortical bone 12a. Once past the anchor hole 30, the set of proximal fins 42 passthrough the cortical bone 12 a and into the cancellous bone 12 b of thescapula S. In one embodiment, the first proximal fin 42 a is positionedin the cortical bone 12 a and the second proximal fin 42 b is positionedadjacent to the cortical bone 12 a.

In order to fully insert the anchor 18 through the anchor hole 30, thestabilizing pins 20 must be aligned with stabilizing holes 32 such thatthe stabilizing pins 20 engage with respective stabilizing holes 32.Thus, as the anchor 18 is advanced into the anchor hole 30, thestabilizing pins 20 are simultaneously advanced into the stabilizingholes 32. Because the stabilizing pins 20 have a substantiallyconsistent diameter and the stabilizing holes 32 are sized to accept thestabilizing pins 20, extra force is not required to advance thestabilizing pins 20 into the scapula S. The glenoid component 10 isadvanced into the scapula S until the second surface 26 of the headportion 16 abuts the glenoid 12 and the anchor 18 and stabilizing pins20 are fully inserted into the scapula S. When the anchor 18 ispositioned through the anchor hole 30 and the stabilizing pins 20 arepositioned through the stabilizing holes 32, the stabilizing pins 20prevent rotation or movement of the glenoid component 10 relative to theglenoid 12.

When the sets of proximal and distal fins 42, 44 of the anchor 18 arepositioned within the scapula S, the proximal and distal fins 42 a, 42b, 44 a, 44 b, 44 c, 44 d are bent towards the glenoid 12, securing theglenoid component 10 to the scapula S. The anchor 18 of the glenoidcomponent 10 is positioned in the scapula S such that the sets of distaland proximal fins 42, 44 are embedded in the cancellous bone 12 b, whichhas low density and strength and fills the inner cavity of the scapulaS. Because the set of proximal fins 42 is located proximate the secondsurface 26 of the head portion 16, the set of proximal fins 42 islocated adjacent and proximate the cortical bone 12 a, which is denseand forms the surface of the scapula S. The first proximal fin 42 aabuts the cortical bone 12 a, providing resistance to prevent the set ofproximal fins 42 from passing through the anchor hole 30 and removingthe anchor 18 from the scapula S. In addition, in the deformed state,the proximal fins 42 a, 42 b also function to stabilize the shaft 34 andprevent the shaft 34 from bending when side loaded. Because the set ofproximal fins 42 substantially continuously abuts against the corticalbone 12 a, the glenoid component 10 provides increased resistance toremoval from the scapula S compared to a glenoid component that does notinclude a set of proximal fins.

In addition, over time, as the glenoid component 10 remains within thescapula S, tissue will grow into the spaces between the fins 42 a, 42 b,44 a, 44 b, 44 c, 44 d and provide further resistance to pulling out theanchor 18 from the anchor hole 30. The combination of the configurationof the sets of proximal and distal fins 42, 44 within the scapula S andthe tissue that grows around the fins 42 a, 42 b, 44 a, 44 b, 44 c, 44 deliminates or reduces the need to use bone cement or other adhesivemeans to secure the glenoid component 10 to the glenoid 12. Likewise,the indents 52 in the bodies 46 of the stabilizing pins 20 also providean area for tissue to grow, further increasing the force required toremove the glenoid component 10 from the scapula S.

Referring back to FIG. 1, once the glenoid component 10 is fixed to theglenoid 12 and the scapula S, the first articulating surface 22 of thehead portion 16 of the glenoid component 10 acts as an articulating orbearing surface for engaging the humeral head 24 of the humeralcomponent 14. The glenoid component 10 thus functions as a replacementfor the natural glenoid of the scapula S, allowing the glenoid component10, the glenoid 12 and the humeral component 14 to interact similarly toa natural shoulder socket.

FIG. 4 shows a side view of an alternative glenoid component 100. Theglenoid component 100 functions substantially similarly to the glenoidcomponent 10 of FIGS. 1 and 2 and includes a head portion 102, an anchor104 and a plurality of stabilizing pins 106 a, 106 b (not shown), 106 c.The anchor 104 includes a shaft 108 having a proximal end 110, a middlesection 112 and a distal end 114. A set of proximal fins 116 extendsradially from the proximal end 110 of the shaft 108 and a set of distalfins 118 extends radially from the distal end 114 of the shaft 108. Thesets of proximal and distal fins 116, 118 are optionally separated bythe middle section 112 of the shaft 108.

The anchor 104 of the glenoid component 100 is substantially similar tothe anchor 18 of the glenoid component 10 of FIGS. 1 and 2 except thateach of the first proximal fin 116 a and the first, second and thirddistal fins 118 a, 118 b and 118 c includes a rib feature 120 to createpreferential deformation of the fins 116 a, 118 a, 118 b and 118 c. Therib features 120 function to transfer load between the proximal fins 116a, 116 b, and between the distal fins 118 a, 118 b, 118 c, 118 d, toreduce fin deformation in response to a removal force 121. For example,when the glenoid component 10 is being pulled away from the glenoid 12(FIG. 1), the rib feature 120 of the first proximal distal fin 116 aabuts the second proximal fin 116 b, reducing deformation arising fromthe removal force 121. Likewise, the rib feature 120 of the first distalfin 118 a abuts the second distal fin 118 b, the rib feature 120 of thesecond distal fin 118 b abuts the third distal fin 118 c and the ribfeature 120 of the third distal fin 118 c abuts the fourth proximal fin118 d, reducing deformation of the respective first, second and thirddistal fins 118 a, 118 b, 118 c in response to the removal force 121.The fins 116 a, 118 a, 118 b, 118 c are substantially uni-directionallydeformable. As used herein, “uni-directionally deformable” or“uni-directional deformation” refer to a structure that deforms in afirst direction, but resists deformation in an opposite seconddirection.

FIG. 5 shows a perspective view of an alternative glenoid component 200.The glenoid component 200 functions substantially similarly to theglenoid component 10 of FIGS. 1 and 2 and includes a head portion 202,an anchor 204 and a plurality of stabilizing pins 206 a, 206 b, 206 c.The anchor 204 includes a shaft 208 having a proximal end 210, a middlesection 212 and a distal end 214. A set of proximal fins 216 extendsradially from the proximal end 210 of the shaft 208 and a set of distalfins 218 extends radially from the distal end 214 of the shaft 208. Theproximal and distal fins 216, 218 are optionally separated by the middlesection 212 of the shaft 208.

The anchor 204 of the glenoid component 200 is substantially similar tothe anchor 18 of the glenoid component 10 of FIGS. 1 and 2 except thateach of the proximal and distal fins 216 a, 216 b, 218 a, 218 b, 218 c,218 d includes one or more cut-outs 220. As the glenoid component 10 ispushed into the scapula S, additional force is needed to pass theproximal and distal fins 216 a, 216 b, 218 a, 218 b, 218 c, 218 dthrough the anchor hole 30. By reducing the surface area of the proximaland distal fins 216 a, 216 b, 218 a, 218 b, 218 c, 218 d, the amount offorce required to insert the glenoid component 10 is also reduced.

In one embodiment, radial cut-outs 220 are machined through all of theproximal and distal fins 216 a, 216 b, 218 a, 218 b, 218 c, 218 d inorder to reduce the surface area. Although FIG. 5 depicts the cut-outs220 as being positioned substantially symmetrically around the anchor204, the cut-outs 220 may be positioned anywhere around the anchor 204without departing from the intended scope of the invention. In addition,there may be any number of cut-outs 220 machined from the proximal anddistal fins 216 a, 216 b, 218 a, 218 b, 218 c, 218 d.

FIG. 6 shows a perspective view of an alternative glenoid component 400.The glenoid component 400 functions substantially similarly to theglenoid component 10 of FIGS. 1 and 2 and includes a head portion 402,an anchor 404 and a plurality of stabilizing pins 406 a, 406 b, 406 c.The anchor 404 includes a shaft 408 having a proximal end 410, a middlesection 412 and a distal end 414. A set of proximal fins 416 extendsradially from the proximal end 410 of the shaft 408 and a set of distalfins 418 extends radially from the distal end 414 of the shaft 408. Thesets of distal and proximal fins 416, 418 are optionally separated bythe middle section 412 of the shaft 108.

The anchor 404 of the glenoid component 400 is substantially similar tothe anchor 18 of the glenoid component 10 of FIGS. 1 and 2 except thatthe proximal end 410 of the shaft 408 of the anchor 404 includes astabilizing boss 420. The stabilizing boss 420 has a diameter D_(B) thatis larger than the diameter D_(S) of the shaft 408 but smaller than thediameters D_(F) of the sets of proximal and distal fins 416, 418. Thestabilizing boss 420 functions to aid in stabilizing the shaft 408 in aradial load condition. In one embodiment, the stabilizing boss 420 has adiameter substantially equal to the diameter of the anchor hole 30D_(AH) (FIG. 3) to help prevent the shaft 408 from bending when sideloaded.

FIGS. 7A and 7B show a perspective view and a side view, respectively,of an alternative glenoid component 500. The glenoid component 500functions substantially similarly to the glenoid component 10 of FIGS. 1and 2 and includes a head portion 502, an anchor 504 and a plurality ofstabilizing pins 506 a, 506 b, 506 c. The anchor 504 includes a shaft508 having a proximal end 510, a middle section 512 and a distal end514. A set of proximal fins 516 extends radially from the proximal end510 of the shaft 508 and a set of distal fins 518 extends radially fromthe distal end 514 of the shaft 508. The proximal and distal fins 516,518 are optionally separated by the middle section 512 of the shaft 508.

The anchor 504 of the glenoid component 500 is substantially similar tothe anchor 18 of the glenoid component 10 of FIGS. 1 and 2 except thatthe diameters of the proximal fins 516 a, 516 b, 516 c are not the same.In the illustrated embodiment, the first and second proximal fins 516 b,516 b have a smaller diameter than the diameter D_(F) of the thirdproximal fin 516 c. The smaller diameters of the first and secondproximal fins 516 a, 516 b function to stabilize the shaft 508 of theanchor 504 and to prevent the shaft 508 from bending from side loading.In one embodiment, the diameters of the first and second proximal fins516 a, 516 b are substantially equal to the diameter of the anchor hole30 D_(AH). Although FIGS. 7A and 7B depict only the first and secondproximal fins 516 a, 516 b as having a different diameter than the restof the proximal and distal fins 516 c, 518 a, 518 b, 518 c, 518 d, anyof the proximal and/or distal fins 516 a, 516 b, 516 c, 518 a, 518 b,518 c, 518 d may have varying diameters.

FIG. 8 shows a perspective view of an alternative glenoid component 600.The glenoid component 600 functions substantially similarly to theglenoid component 10 of FIGS. 1 and 2 and includes a head portion 602,an anchor 604 and a plurality of stabilizing pins 606 a, 606 b, 606 c.The anchor 604 includes a shaft 608 having a proximal end 610, a middlesection 612 and a distal end 614. A set of proximal fins 616 extendsradially from the proximal end 610 of the shaft 608.

The anchor 604 of the glenoid component 600 is substantially similar tothe anchor 18 of the glenoid component 10 of FIGS. 1 and 2 except thatthe anchor 604 does not include a set of distal fins. Thus, the middlesection 612 and the distal end 614 of the shaft 608 are smooth with noradial extensions. The embodiment shown in FIG. 8 illustrates thatdistal fins are not required to fixate the glenoid component 600 to theglenoid 12 (FIG. 1). When the anchor 604 does not include any distalfins, initial fixation can still be achieved using only the set ofproximal fins 616.

FIG. 9A shows a perspective view of an alternative glenoid component700. The glenoid component 700 functions substantially similarly to theglenoid component 10 of FIGS. 1 and 2 and includes a head portion 702,an anchor 704 and a plurality of stabilizing pins 706 a, 706 b, 706 c.The anchor 704 has a diameter DA and includes a shaft 708 having aproximal end 710, a middle section 712 and a distal end 714. A set ofproximal fins 716 extends radially from the proximal end 710 of theshaft 708 and has a diameter D_(F).

The anchor 704 of the glenoid component 700 is substantially similar tothe anchor 18 of the glenoid component 10 of FIGS. 1 and 2 except thatrather than having a set of distal fins extending radially from thedistal end 714 of the shaft 708, the distal end 714 includes a pluralityof grooves 718 a, 718 b, 718 c, 718 d (collectively referred to as“grooves 718”) machined into the shaft 708. The grooves 718 may bemachined into the distal end 714 of the shaft 708 by any means known inthe art. In one embodiment, the grooves 718 are machined into the shaft708 by step drilling. Similar to the glenoid component 600 shown in FIG.8, initial fixation of the anchor 704 of the glenoid component 700 canstill be achieved using just the set of proximal fins 716. After theinitial fixation, long term fixation is achieved through bone in-growthinto the grooves 718. Although FIG. 9 depicts the distal end 714 of theshaft 708 as including four grooves 718, the distal end 714 of the shaft708 may include any number of grooves.

FIG. 9B shows a side view of a stepped hole configuration 800 createdthrough the cortical bone 12 a and within the cancellous bone 12 b. FIG.9C shows a side view of the anchor 704 of the glenoid component 700positioned within the stepped hole configuration 800. The stepped hole800 is sized to receive the anchor 704 of the glenoid component 700 andinitially reduce the amount of force required to insert the anchor 704of the glenoid component 700 into the scapula S. The stepped hole 800includes a proximal portion 802 having a first diameter SH₁ and a distalportion 804 having a second diameter SH₂ bone 12 b. The proximal portion802 is located through the cortical bone 12 a and the cancellous bone 12b and the distal portion 804 is located within the cancellous bone 12 b.The first diameter SH₁ is greater than the second diameter SH₂ andslightly smaller than the diameter D_(F) (FIG. 9B) of the set ofproximal fins 716. The second diameter SH₂ is substantially the samesize as the diameter DA of the anchor 704, allowing easily insertion ofthe distal end 714 of the anchor into the stepped hole 800. Because thediameter D_(F) of the set of proximal fins 716 is greater than the firstdiameter SH₁ of the stepped hole 800, as the proximal end 710 of theanchor 704 is inserted into the stepped hole 800, there is “lock-up” ofthe set of proximal fins 716 under the cortical bone 12 a.

Once the anchor 704 is positioned in the stepped hole, the relativesizes of the second diameter SH₂ of the stepped hole 800 and the anchorDA allows for bone ingrowth into the recessed grooves 718 at the distalend 714 of the shaft 708. Although the stepped hole 800 is discussedwith relation to glenoid component 700, the stepped hole 800 may be usedwith other glenoid components in which the proximal end of the anchorhas a greater diameter than the distal end of the anchor. For example,the stepped hole configuration 800 may also be used with the glenoidcomponent 600 shown in FIG. 8. In one embodiment, the step hole 800 isformed using a step drill. FIG. 10 shows an exploded side view of analternative glenoid component 300. In order to accommodate patients ofvarious shapes and sizes, the glenoid component 300 may have a modulardesign. The glenoid component 300 functions substantially similarly tothe glenoid component 10 of FIGS. 1 and 2 and includes a head portion302, an anchor portion 304 and a plurality of stabilizing pins 306 a,306 b (not shown), 306 c. The head portion 302 is preferably a singlepiece of material, while the anchor portion 304 is formed of a pluralityof modular pieces.

In the embodiment shown in FIG. 10, the anchor portion 304 includes afirst spacer 308, a first proximal fin 310 a, a second proximal fin 310b, a second spacer 312 and a set of distal fins 314. The first spacer308 sets an offset between a second surface 326 of the head portion 302and the first proximal fin 310 a corresponding generally to a thicknessof the cortical bone 12 a (FIG. 3).

Each of the modular pieces 308, 310 a, 310 b, 312, 314 of the anchorportion 304 includes a bore 316 running through the center of the pieces308, 310 a, 310 b, 312, 314 such that they can be maintained togetherand fixed to the head portion 302 by a screw 318. Although FIG. 10 showsthe glenoid component 300 as including the modular pieces 308, 310 a,310 b, 312, 314, the glenoid component 300 may include any number ofmodular pieces without departing from the intended scope of the presentinvention. For example, the glenoid component 300 may include additionalspacers to accommodate a patient with larger proportions or may includeonly one spacer to accommodate a patient with smaller proportions.Various spacers may also be provided having varying thicknesses. Inanother embodiment, additional fins may be included adjacent the set ofdistal fins 314 or one of the proximal fins 310 a, 310 b.

The embodiment of FIG. 10 is particularly well suited for building theglenoid component 300 from multiple materials. For example, the headportion 302 can be made from a first material and one or more of theother pieces 308, 310 a, 310 b, 312, 314 can be made from one or moresecond materials. Forming the pieces 308, 310 a, 310 b, 312, 314separately also facilitates formation of various structures to achieveuni-lateral deformation.

While each of the embodiments of FIGS. 4 through 10 are discussed asseparate, alternative glenoid components to the glenoid component 10shown in FIGS. 1-3, the individual structural features of each of theembodiments may be incorporated into any glenoid component. For example,the glenoid component 700 (FIG. 9) having the distal grooves 718 mayalso include the stabilizing boss 420 (FIG. 6) or the proximal fins 516a and 516 b having decreased diameters (FIG. 7) for increased stability.

EXAMPLES

The present invention is more particularly described in the followingexamples that are intended as illustrations only, since numerousmodifications and variations within the scope of the present inventionwill be apparent to those skilled in the art.

Example 1—Insertion

FIG. 11 illustrates the load versus displacement of a glenoid componentof the present invention and the load versus displacement of acomparative glenoid component during insertion into a foam structuredesigned to exhibit similar density properties of a scapula. The foamstructure included an anchor hole for accepting an anchor of the glenoidcomponent of the present invention and an anchor of the comparativeglenoid component.

The glenoid component of the present invention included an anchor havinga set of four distal fins extending from a distal end of the anchor anda set of two proximal fins extending from a proximal end of the anchor.The set of distal fins and the set of proximal fins are separated by amiddle section of the anchor, such as illustrated in FIG. 2. The set ofproximal fins were offset from a rear surface of the head portion byabout 2.5 millimeters.

The comparative glenoid component was substantially similar to theglenoid component of the present invention except that the comparativeglenoid component did not include a set of proximal fins positioned toengage with the cortical bone. The comparative glenoid componentincluded only a set of four distal fins.

As can be seen in FIG. 11, the force required to advance the distal endof the glenoid component of the present invention and the distal end ofthe comparative glenoid component into the foam structure wascomparable. Initially, the distal fins on both glenoid componentscontacted the anchor hole of the foam structure. To advance each of thedistal fins through the anchor hole, the amount of force that wasapplied to the glenoid component increased, creating a first spike, asecond spike and a third spike corresponding to the location of thefirst, second, and third distal fins along the distal end of the anchor.

As the glenoid component of the present invention was advanced furtherinto the foam structure, however, the amount of force required toadvance the anchor through the anchor hole increased in response to thefirst and second proximal fins engaging the anchor hole. The amount offorce required to advance the proximal fins into the foam structureincreased sharply as the first proximal fin and then the second proximalfin contacted the anchor hole, spiking to a required load of about 44.5pounds and 39.5 pounds, respectively.

By contrast, the comparative glenoid component did not requireadditional force to advance the proximal end of the anchor into theanchor hole. Rather, the amount of force required to advance thecomparative glenoid component into the foam structure steadily decreasedto about 10 or about 11 pounds. On average, the glenoid component of thepresent invention required about 75% more force to insert the proximalend of the anchor through the anchor hole than required to insert theproximal end of the anchor of the comparative glenoid component throughthe anchor hole.

Example 2—Removal

FIG. 12 illustrates the load versus displacement of the glenoidcomponent of the present invention and the load versus displacement ofthe comparative glenoid component during removal from the foamstructure.

As can be seen in FIG. 12, the initial force required to pull theglenoid component of the present invention out from the foam structurespiked to about 39 pounds in the first millimeter of displacement,followed immediately by a spike of about 43.5 pounds at about 2millimeters of displacement. In particular, a force of about 39 poundswas required to pull the first proximal fin through the anchor hole anda force of about 43.5 pounds was required to pull the second proximalfin through the anchor hole. These spikes all occurred within about 2millimeters of displacement of the glenoid component of the presentinvention.

By contrast, the initial force required to move the comparative glenoidcomponent relative to the foam structure increased more gradually, andonly to an initial force of about 24 pounds within about 2 millimetersof displacement. It was not until the comparative glenoid component wasdisplaced about 7.5 millimeters that the first distal fin engaged theanchor hole and increased the removal force to about 34 pounds.

As a practical matter, once the comparative glenoid component wasdisplaced about 7.5 millimeters, the structural integrity of theprosthesis was compromised. The spike of about 34 pounds at 7.5millimeters of displacement was too late to save the implant.

The glenoid component of the present invention provided a force about71.5% greater than the comparative glenoid component, over less thanhalf the displacement. As a result, the present glenoid componentprovided a significantly greater resistance to initial displacement thanthe comparative glenoid component.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimit of that range and any other stated or intervening value in thatstated range is encompassed within the inventions. The upper and lowerlimits of these smaller ranges which may independently be included inthe smaller ranges is also encompassed within the inventions, subject toany specifically excluded limit in the stated range. Where the statedrange includes one or both of the limits, ranges excluding either bothof those included limits are also included in the inventions.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which these inventions belong. Although any methods andmaterials similar or equivalent to those described herein can also beused in the practice or testing of the present inventions, the preferredmethods and materials are now described. All patents and publicationsmentioned herein, including those cited in the Background of theapplication, are hereby incorporated by reference to disclose anddescribed the methods and/or materials in connection with which thepublications are cited.

The publications discussed herein are provided solely for theirdisclosure prior to the filing date of the present application. Nothingherein is to be construed as an admission that the present inventionsare not entitled to antedate such publication by virtue of priorinvention. Further, the dates of publication provided may be differentfrom the actual publication dates which may need to be independentlyconfirmed.

Other embodiments of the invention are possible. Although thedescription above contains many specificities, these should not beconstrued as limiting the scope of the invention, but as merelyproviding illustrations of some of the presently preferred embodimentsof this invention. It is also contemplated that various combinations orsub-combinations of the specific features and aspects of the embodimentsmay be made and still fall within the scope of the inventions. It shouldbe understood that various features and aspects of the disclosedembodiments can be combined with or substituted for one another in orderto form varying modes of the disclosed inventions. Thus, it is intendedthat the scope of at least some of the present inventions hereindisclosed should not be limited by the particular disclosed embodimentsdescribed above.

Thus the scope of this invention should be determined by the appendedclaims and their legal equivalents. Therefore, it will be appreciatedthat the scope of the present invention fully encompasses otherembodiments which may become obvious to those skilled in the art, andthat the scope of the present invention is accordingly to be limited bynothing other than the appended claims, in which reference to an elementin the singular is not intended to mean “one and only one” unlessexplicitly so stated, but rather “one or more.” All structural,chemical, and functional equivalents to the elements of theabove-described preferred embodiment that are known to those of ordinaryskill in the art are expressly incorporated herein by reference and areintended to be encompassed by the present claims. Moreover, it is notnecessary for a device or method to address each and every problemsought to be solved by the present invention, for it to be encompassedby the present claims. Furthermore, no element, component, or methodstep in the present disclosure is intended to be dedicated to the publicregardless of whether the element, component, or method step isexplicitly recited in the claims.

What is claimed is:
 1. A glenoid prosthesis for securement to a glenoidof a patient, the glenoid prosthesis comprising: a head portioncomprising a convex rear surface configured to engage the glenoid and anarticular surface opposite the convex rear surface that is configured toengage with a humeral component; an anchor member extending from theconvex rear surface of the head portion, the anchor memberintegrally-formed with the convex rear surface of the head portion; anda plurality of deformable fins extending radially outward from theanchor member, the plurality of deformable fins including a firstplurality of fins and a second plurality of fins that are spaced apartfrom the first plurality of fins by a middle section of the anchormember, wherein the first plurality of fins comprises a firstcancellous-bone-engaging fin which extends radially outward from adistal end of the anchor member, wherein the firstcancellous-bone-engaging fin is sized and configured to be positionedwithin cancellous bone of the glenoid when the convex rear surface ofthe head portion engages the glenoid, wherein the second plurality offins comprises a first cortical-bone-engaging fin which extends radiallyoutward from a proximal end of the anchor member and is located adjacentto the convex rear surface of the head portion, wherein the firstcortical-bone-engaging fin is sized and configured to be positionedwithin cortical bone of the glenoid when the convex rear surface of thehead portion engages the glenoid.
 2. The glenoid prosthesis of claim 1,wherein the anchor member is positioned at a center of the convex rearsurface of the head portion.
 3. The glenoid prosthesis of claim 1,wherein a second fin of the second plurality of fins is offset from theconvex rear surface of the head portion by a distance of about 2millimeter or less, wherein said second fin of the second plurality offins is sized and configured to abut the cortical bone of the glenoidwhen the convex rear surface of the head portion engages the glenoid. 4.The glenoid prosthesis of claim 1, wherein at least one of the pluralityof deformable fins is uni-directionally deformable.
 5. The glenoidprosthesis of claim 1, further comprising a stabilizing pin extendingfrom the convex rear surface of the head portion, the stabilizing pinadapted to prevent rotation of the head portion relative to the glenoid.6. The glenoid prosthesis of claim 1, wherein the first plurality offins includes fins having a different diameter than fins of the secondplurality of fins.
 7. The glenoid prosthesis of claim 1, wherein thedistal end of the anchor member includes a plurality of grooves.
 8. Theglenoid prosthesis of claim 1, wherein the first plurality of finscomprises a greater number of fins than the second plurality of fins.